Welcome to the Forum. You have a 38 Double Action, 4th Model revolver. It would have shipped from the factory somewhere around 1904 to 1906. These revolvers take 38 S&W ammo. I think European ammo is called 38 Corto. The 4th Model was made from 1895 to 1909 between 322,701 and 539,000. These guns were popular in South America long after the US market started drying up with the advent of the 38 Hand Ejector models. 6" barrels are somewhat uncommon, since the popular lengths were shorter for easy carry.